A number of medical procedures have been developed which access the vascular system. Such procedures include arteriography, aortography, angiography, and angioplasty, for example. Catheters of many different designs have been developed for these procedures.
The complexity of some of these catheter devices has made it difficult to pass them down the often tortuously convoluted paths of blood vessels. Consequently, additional tools have been developed for the purpose of aiding the passage of a catheterization device through the vessel. Among these devices are guidewires available commercially from various vendors.
Typically, the vascular system is accessed with an introducer which can be a relatively large bore hypodermic needle. The guidewire is passed down the needle bore into the vessel and is threaded through the vessel. The introducer needle is then withdrawn. To assist in passing the guidewire through the vessel, it may be equipped with means to stiffen it and/or steer the tip around curves in the vessel. When the tip of the guidewire is at the desired location, the catheter can be passed over the guidewire to the site. With the catheter in place, the guidewire can be withdrawn, and the procedure requiring the conduit for the catheterization can be carried out.
Commercially available guidewires constructed for the purpose just described are typically a few hundredths of an inch in diameter and consist of an elongated, flexible., tightly wound helical coil spring. A wire stylet carried within the lumen of the coil can be used to stiffen and steer it. The guidewire is typically made of stainless steel with a rounded and polished end weld closure.
Such helical coil springs, like those serving as guidewires in the aforesaid applications, can also be adapted, by simply leaving the end open, to function as flexible infusion wires to deliver contrast media for radiographic identification or other liquid to a selected site in the body. These devices are also available in commerce. They generally deliver a liquid at the rate of about 1-3 ml/sec under pressures in the range of about 0-250 psi; flow is out through the open end only.
The catheter of this invention is designed to facilitate the slow infusion delivery of a therapeutic fluid at a distant localized site of diseased tissue. The inventive catheter utilizes, as one of its elements, a helical coil spring guidewire with a sealed distal tip. Several pieces of prior art disclose catheterization devices which utilize guidewire-like structures.
U.S. Pat. No. 3,757,768 discloses a helical coil spring guidewire adapted for use as a catheter by including an inert plastic material on the entire outer surface of the spring which extends beyond the distal end of the spring to define a hollow tip which is perforated to deliver a fluid.
U.S. Pat. No. 3,922,378 is closely related to the aforesaid '768 patent in that it describes a method for applying a fluorinated hydrocarbon film to a flexible coil spring guidewire.
U.S. Pat. No. 4,405,314 discloses the use of a guidewire having a J-curvature at its distal end in conjunction with an introducer to enlarge a drainage tract created in the performance of a percutaneous nephrostomy. The guidewire is not the source of a medicament.
U.S. Pat. No. 4,821,722 describes a self-venting balloon dilatation catheter which utilizes at its distal tip a coil spring which has attributes of the guidewire described hereinabove, but it does not deliver a therapeutic fluid.
U.S. Pat. No. 4,994,033 discloses an intravascular catheter designed to apply liquid medication to a stenotic lesion in a blood vessel. The catheter is equipped with a guidewire which plays no direct role in delivering the medication.
U.S. Pat. No. 5,021,044 describes a multilumen vascular catheter for the delivery of a thrombolytic fluid to a blood vessel. The catheter is equipped with a central guidewire which facilitates advancement of the catheter in the blood vessel but is not directly involved in delivery of the therapeutic fluid.
U.S. Pat. No. 5,087,244 describes a catheter for the localized slow delivery of a medication through a balloon having minute holes in it. The catheter includes a central guidewire which has no direct role in delivering the medication.
Whereas elongated, flexible, tightly wound helical coil springs are disclosed in several capacities within the catheter context, none of these disclosures suggests the adaptation of such a helical coil spring for the slow, localized perfusion of a diseased tissue site with a therapeutic fluid. The medical literature suggests that such localized perfusion of diseased tissue can offer distinct advantages over other treatments.
For example, in the field of oncology, the use of chemotherapy systemically in the treatment of cancers is limited in many cases to utilizing very low concentrations of the therapeutic agent because of the cytotoxicity of the fluid when it is delivered into the blood stream. Direct intratumoral or loco-regional chemotherapy may permit the use of much higher concentrations of the therapeutic agent. In addition, bolus injections of the therapeutic agent, leading to spikes and valleys in the concentration of the medication over time may be avoided by continuously perfusing the tumorous region with the drug. In spite of these logical advantages, localized intratumoral chemotherapy has been largely overlooked.
In this regard, attention is directed to H. Brincker, M.D., Critical Reviews in Oncology/Hematology, 15 (1993) pp 91-98, in which the point is made that intratumoral chemotherapy is not even mentioned in major standard textbooks on chemotherapy and cancer treatment. Among the results of clinical studies summarized in this article are the following: Randomized trials involving a total of 411 patients with hepatic metastases from colorectal carcinoma showed significantly higher response and survival rates with intrahepatic as opposed to systemic infusion with the cancer drug FUDR. Intratumoral injections of the cytostatic agent thio-TEPA in 131 patients with advanced breast cancer resulted in improvement in 66% of the cases, while administration by the i.v. route was less effective.
Furthermore, it is reported that several studies of the intratumoral injection of bleomycin in patients with head and neck tumors have shown very promising results. Treatment of a variety of inoperable, deep-seated intraabdominal tumors with various chemotherapeutic agents injected directly into the tumors also led to promising results without systemic toxicity. The author of the aforesaid article concludes that "Both clinical and experimental studies show consistently that intratumoral chemotherapy leads to consistently higher concentrations of cytostatics in the target tissues than conventional i.v. chemotherapy, thus confirming the rationale for this treatment."
It is to be expected that increasing the local concentration of the therapeutic agent in the treatment of other types of diseased tissue will also lead to improved results. For example, it is likely that localized perfusion with an appropriate therapeutic agent will also improve the cure rate in the treatment of non-healing, ulcerous wounds.
Electrochemotherapy (ECT) and electrical impulse chemotherapy (EIC), in which a cancerous tumor is treated with a chemotherapeutic agent in the presence of an electric field applied across the tumor, has also yielding very promising results; see, e.g., S. Dev and G. Hofmann, Cancer Treatment Reviews, 20 (1994) pp 105-115. Electrically conductive catheters, such as those disclosed herein, can play an important role in such therapy.